Argonne National Laboratory swaps out key component in liquid metal test loop.
April 23, 2025
minute read time
Argonne National Laboratory successfully swapped out a key component in its liquid metal test loop that’s being used to advance a new class of reactors.
The new upgrade is the first of its kind in the United States in more than 30 years and will help inform the design and operation of sodium-cooled fast reactors that are currently being developed by several U.S. companies.
Out with the Cold (Trap)
Argonne researchers recently replaced an aging cold trap device on its Mechanisms Engineering Test Loop (METL) that is used to purify more than 750 gallons of reactor-grade sodium.
METL is the largest liquid metal test facility for sodium-cooled fast reactors in the United States and is training a new crop of workers to operate them.
Fast reactors can be designed to run on recycled fuel from other reactors to drastically improve the fuel efficiency, waste reduction, and overall performance of nuclear power plants.
The United States hasn’t operated a fast reactor since the Experimental Breeder Reactor II shut down in the mid 90s, but projected increases in power demands have many companies revisiting the technology.
METL first started operations in 2018 to help advance research on liquid metal technologies and is currently being used by industry partners to test different components for potential use in their designs.
The cold trap is an essential piece to any liquid metal reactor design to help filter out oxide impurities present in the sodium that is used to cool the reactor. If not controlled, these impurities could cause accelerated corrosion of the systems and lower flow rates, resulting in degraded performance.
Replacing the device was required to meet the design specifications of future experiments and played a key role in regaining U.S. experience on replacing sodium loop components.
“It’s exciting,” said Dr. Matthew Weathered, a principal nuclear engineer. “The METL team is revitalizing and developing these key operations and maintenance techniques to ensure we are able to deploy U.S. sodium cooled reactors in the near future.”
The METL facility utilizes welded construction techniques that are consistent with the maintenance of any advanced liquid metal reactor.
The sodium in the cold trap was frozen and cut out of the system before a new cold trap was welded onto the sodium piping.
The lab consulted with French Alternative Energies and Atomic Energy Commission prior to performing the maintenance.
The entire process took two weeks to complete after months of planning, while the rest of the test loop remained hot, molten, and in operation.
COMING SOON
METL plans to expand its testing capabilities in 2026 by activating a fifth test vessel to accommodate additional liquid metal tests.
The cold trap replacement was funded through the U.S. Department of Energy’s National Reactor Innovation Center (NRIC), which funds the operations and maintenance activities at the METL facility.
NRIC works to build or enhance the Department’s infrastructure to enable the successful deployment of advanced nuclear technologies.
Learn more about NRIC.